Electric zinc-distilling furnace.



J. THOMSON & F. A. J. FITZ GERALD. ELECTRIC ZINC DISTILLING FURNACE.

APPLICATION FILED JUNE 21, 1916.

1,21 9,1 94. Patented Mar. 13, 1917.

3 SHEETS-SHEEI I.

J. THOMSON & F. A. J. FlTZ GERALD.

ELECTRIC ZINC DISTILLING FURNACE.

APPLICATION FILED JUNE 21, 1916- 3 SHEETSSHEET 2.

Patented Mar. 13, 1917.

v1 00 mfo'zs J. THOMSON & F A. I. FITZ GERALD.

ELECTRIC ZINC DISTILLING FURNACE.

APPLICATION FILED IUNEZI, I916.

Patented Mar. 13, 1917.

3 SHEETSSHEET 3L UN Y UNITED STATES PATENT OFFICE."

JOHN THOMSON, OF NEW YORK, AND FRANCIS A. J. FITZ GERALD, OF NIAGARAFALLS, NEW YORK, ASSIGNORS TO JOHN THOMSON PRESS COMPANY, OF JERSEYCITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

ELECTRIC ZINC-DISTILLING FURNACE.

Application filed June 21, 1916.

To all whom it may concern:

Be it known that we, JonN Thomson and FnANcis A. J. Frrz GnnALn,citizens of the United States, and residents, respectively, of theborough of Manhattan, city of New York, county and State of New York,and of Niagara Falls, county of Niagara, State of New York, haveinvented certain new and useful Imprm'ements in Electric Zinc-DistillingFurnaces, of which the following is a specification, reference beingmade to the accompanying drawings, forming a part hereof.

This is an invention relating to the metallurgy of zinc, and itparticularly pertains to an apparatus for the purification of speltercontaining deleterious metals, such as lead, iron and cadmium, bydistillation in an electric furnace. The objects of the invention are toconstruct an apparatus in a manner to minimize the cost of transformingmetal into fu-me or gaseous vapor, to retain cer-- tain elements of thefume within the furnace and to then evacuate and conduct other portionsof the fume, viz., portions which are at the lowest permissibletemperature, to any suitable means for liquid condensation, or forprecipitation as dust, or for burning to an oxid.

In the accompanying drawings, which constitute a part of thisspecification there is illustrated a preferred but not necessarily anexact detail mode of realizing the invention.

Figure 1 is a vertical transverse center section, viewed as denoted bythe arrow on line A of Figs. 2 or 3; Fig. 2 is a vertical longitudinalcenter section, viewed as denoted by the arrow on line B of Figs. 1 or3; Fig. 3 is a top plan, the cover and several of the upperseptum-plates being omitted, and Fig.

I 4 is a detail showing a feature of construction less clearly shown inthe necessarily smaller scale of the assembled drawings.

The heating system of the furnace needs only be here described in so faras will incorporate it as an element in combination with the novelfeatures of the invention. Thus, it is comprised in a suspended carbonresistor, C, shown as the zig-zag type, attached by a connector, 5, forelectrification Specification of Letters Patent.

Patented Mar. 13, 1917. Serial No. 104,838.

in series, when incited through the terminals, (5, 7, from thediagrammatically illustrated source of energy 8.

Beneath the resistor is a trough, or tank 9, which contains the bath ofmolten metal, as 10, usually supplied through a spout, indicated by thedotted lines, 12, Fig. 2.

In furnaces having a zig-zag type of resistor as hitherto constructed,the operation and result were such that the fume flowed directlyupwardly from the bath, through the zig-zag slots and around the sidesof the resistor and thence through superhuposed slotted or portedseptums, the latter acting to somewhat conserve the heat emitted by theupper surface of said resistor. But as the area of the bath wasrelatively large and as the rate of fumeflow was also correspondinglylow or sluggish, the fume became super-heated, its temperature in factapproximating that of the resistor. However, some portions of thissuper-heat were dissipated by causing the fume to pass along horizontalseptum-spaces and in contact with the walls and roof of the furnace.

It will here be noted that while the temperatures at which variousmetals will boil have been rather accurately determined, as, say, theconventional figures of 930 for zinc and 1800 C. for lead, variousconflicting phenomena are observable when the fume of several metals arecombined, as in the instance of combining metals as an alloy. Thus, alarge volume of zincfume may carry with it a minor volume of lead-fumealthough the ten'iperature of the resistor may not exceed 1,300 to1,400" C- ()u the other hand, given two metals. that having the higherfuming temperature will also condense at the higher temperature.

It has been proven in practice. as was primarily theoreticallypredicated, to be of the highest importance not only to avoid hot-spotson the bath, due to the direct action of the resistor, but that the flowof fume from is surface must be uniformly distributed. In other words itis important that a constant amount of fume be emitted from each squareinch of the exposed surface of the bath. If not, those portions of thefurnace walls, as shown.

the bath from which fume passes off most slowly will absorb an excess ofheat-units and thus become in fact hotter than other portions from whichfume escapes more freely.

Again, the facility with which zinc-fume can be rapidly condensed, inlarge volume, is considerably a function of its tempera ture. Thus, iffume enters the condenser at a temperature of, say, 1,300 C., about 350must be emitted to atmosphere before the critical point is approximated,whereas if the fume enters at about 950 the initial condensingtemperature may be almost immediately reached.

The foregoing premises are to be kept in mind as relates to theconstruction and functioning of the remaining features of the furnacenow to be described.

The resistor and is connector is ineased, or boxed-in, except at thelower side, by two vertical aprons or septumplates. 13, 1 supported onstruts, 15, 1(3, anchored in the furnace walls, and an over-lyinghorizontal septum, 17, which rests upon the side septums. The latter areset so as to leave vertical spaces, or fines, 18, 19, along the sidewalls of the furnace and also to provide spaces, or ports, 20, 21,beneath their lower edges and contiguous to the space between the top ofthe trough and the surface of the bath. Upon the horizontal septum, 17,is preferably laid a layer of granular charcoal or petroleum coke,Again, above the coke is an upper septum, composed of plates, as 23,which may be supported by One end of these plates is partially cut awayto form a series of ports. as 24, overlying either set of the verticalfiues, or whichever set that is opposite from the exit to the condenser.Over the upper-septum is a large fume chamber, P, inclosed by arelatively thin cover, formed of plates, 25, and leading from the saidchamber is a throat, 26, through which fume eventually passes to anysuitable means for condensing, not shown but indicated by the dottedoutline, J.

It will now be perceived that the fume within the resistor-boxing isimprisoned, dead, serves as a blanket or envelop" for the resistor, andcannot flow therefrom; the only escape for the evolved bath-fume beingright and left along its surface, as arrows a, thence vertically throughfine 18 and the ports, as arrows c, 2', also vertically through flue 19,thence horizontally along the intermediate space, R, between thehorizontal septums, as arrows d, e, h, and finally again verticallythrough the ports, 24, whereat it commingles with the fume from fine 18.v

The coolest fume is that first rising from the bath, thence escaping tothe side flues and this, at its liberation, is probably not over 950 C.

In flowing across the bath, however, and thence. up through the fines,additional heat is absorbed.

The hottest fume is that immediately in contact with the resistor andsurrounding boxing; which, being a gas, is perfectly transparent to theradiant heatfrom the resistor and also being a very poor thermalconductor gives little heat to the fume rising from the bath butprevents that fume from coming in contact with the resistor, whereat itwould become superheated.

N0 heat directly radiated from the resistor reaches the furnaceside-walls, as the impingement is upon the inner surfaces of its casing;hence the heat imparted to the furnace walls is largely confined to thatcontained in the up-fiowing fume.

The areas of the side-fines and the intermediate horizontal septumchambe are to be such that a relatively rapid flow of fume must occurtherein.

As is well known, granular charcoal or coke is a good non-conductor ofheat. Hence, this acts to insulate the septum; energy is therebyconserved in the resistor. Due to the layer of granular charcoal or cokethe horizontal space, R, can become a cooling chamber for the fume whichpasses through said space. The heat imparted to the upper septum plates,23, is largely that conveyed by the fume. The charcoal or coke, as thecase may be, also serves another desirable purpose. At the starting of agreen furnace, a certain quantity of CO, or water-gas, H,O+C:H,+(70,will be formed and the charcoal or coke will serve to wash out anycontained. air thus preventing or minimizing the formation of ZnO.

As will be observed, the ports, '24:, are located along the side of thefurnace opposite from the condenser or the ports leading to thecondenser; the upper fume-chamber is of large volumetric capacity,relative to the lower spaces and chambers, and the primary cover isquite thin relatively to the furace walls. In this wise, by a properselection, and application thereon, of heat-insulating bricks, as 27,two advantageous conditions are obtained; first, a very slowdisplacement of the fume from this upper cooling chamber and, second,the opportunity to control, by means of the cover, the temperature offume at its exit through the throat,

as arrow m.

The consequences of the foregoing construction, and the conditionsthereby ensuing, are that any lead-fume entrained with the zinc-fume issubjected both to a condens ing temperature and also, which is of equalimportance, it is brought into physical contact with an ample coalescingsurface, whereby liquefied lead is entrained within the furnace anddrips back into the bath. To facilitate the flow of condensed lead, theupper surfaces of the horizontal septums may be given a slight slope,downwardly toward its ports, 24, as is shown in Fig. 1.

The greater the difference of temperature between the resistor and thebath, the higher will be the thermal efficiency. This axiomaticstatement points to important contingent advantages, namely: the rate offuming may be carried on at a rate which would not otherwise bepermissible; the residuum need not be so frequently withdrawn, throughthe tap-opening 28, Fig. 2, as if the primary fuming of lead had to bemore carefully safe-guarded, and the capacity and endurance of any givencondenser is substantially enhanced.

Zinc-fume is exceedingly penetrative and effective heat insulatingbricks are very porous. As a consequence, in starting up a greenfurnace, much spelter is lost by absorption, even to the extent of tonsof metal. Many unsuccessful efforts have been made. to minimize or avoidthis. A satisfactory, simple and inexpensive solution has been found inthe expedient of applying between the chamber wall or walls, as 29, andouter courses of bricks, as 30, and also beneath the bottom of thetrough. relatively thin plates of molded crucible mixture (graphite andclay) or amorphous carbon, as 31, 32, of as large surface as canconveniently be manufactured, their contiguous edges being joined by asystem of, or analogous to that of shipq'oints. By forming the laps ofthese joints at a slight angle, as 33, Fig. 4, to the axis of the facesof the plates, as also the end-joints, 34, they are thus caused, whenconfined by the brick-courses, to firmly interlock, while anycontraction Within the plates serves to tighten the laps on their bevelsand any expansion also tightens by the direct pressure of the transverseabutting ends. This or any similar form of ship-joint can be easilymolded or machined with a considerable degree of accuracy, therebyrealizing a very effective barrier to the escape of both fume or liquidmetal. The advantage of this barriersheathing is not confined to themetal primarily saved, as a furnace so provided can be more quickly putinto full operation.

Various of the details, as illustrated in the drawings, may be modifiedwithout evasion of the essential functions. Thus, for example,baffle-plates may be set in the upper chamber, whereby to effect asinuous flow of fume from the ports to the throat, and vertical finesmight also be provided at either or both of the end-Walls as Well as atthe side-walls of the furnace. So, too, under certain circumstances, asby the use of a thicker layer of granular or powdered carbon on the topof the resistor-casing, the upper septum may be omitted.

What is claimed is:

1. In an electric furnace, a suspended resistor embraced by an overheadhorizontal and vertical side septums, so disposed within the mainchamber as'to provide fume-passages between the furnace walls and alongthe top of the horizontal septum.

2. In an electric distilling furnace, a suspended resistor facing avolitizable bath, a suspended trough or casing surrounding the top andsides of the resistor, vertical uprising fiues between the sides of thecasing and the furnace-walls and connecting spaces beneath the loweredges of the casing, whereby vaporized products are trapped in thecasing but are otherwise free to escape.

3. In an electric. furnace, a suspended rcsistor whose top and sides areincascd by a horizontal and two vertical septums, vertical fume-finesbetween the. side-septunls and the furnace walls and aSll])Ollll'l[)()S0(l horizontal ported septum forminga fume-chamberbetween it and the roof of the. furnace, whereby the. rising fume passesfrom the lines through the septum ports and thence into said chamber.

4. In an electric furnace, an open bottomed septum casing, suspendedwithin the main furnace chamber, within which is a. suspended resistor.and an underlying volatilizable charge, whereby the gases or fumescollected in the said septum-casing cannot be displaced.

5. In an electric zinc distilling furnace, a resistor casing, open atits bottom and having an overlying layer of granular carbon, such ascharcoal or petroleum coke.

6. In an electric zinc. furnace, a resistor casing surrounding the topand sides of a downwardly radiating resistor, an underlying bath, spacesbeneath the lower edges of the casing and open fiues between the sidesof the casing and the furnace walls which communicate with the upperportion of the furnace chamber, the latter having a throat leading to acondenser.

7. In an electric furnace for distilling zinc, a resistor enveloped bynon-displaceable fume contained in a casing open at its bottom, above abath of metal, and having spaces below its edges and fines along itsouter sides, whereby the evolved fume traverses across the lower zoneof'trapped fume and thence rises vertically through the fines.

8. An electric furnace for refining zincfume contaminated withlead-fume, comprised in a bath over which a resistor is suspended andenveloped by undisplaceable fume, a system of vertical uprising sideflues contiguous to the furnace walls leading to over-head enlargingspaces, whereby there is a cumulative reduction in the velocity of flowand the temperature of the fume prior to its entering the condenser.

9. In an electric furnace, means for securing the envelopment of aresistor with un-- displaceable zinc-fume, means for permitting a freeupward escape of evolved fumes or gases from an underlying charge andmeans for progressively reducing the velocity of flow and also thetemperature of the volatilized matters, whereby that substance which hasthe highest condensing temperature will be retained within the furnace.

1(). In an electric furnace, a resistor septum-casing for enveloping theresistor with undisplaceable fume or vapor which rises from anunderlying charge, said casing be ing mounted upon a plurality of spacedstruts or supports .in such manner as to provide free spaces along itslower edges and between its sides and the furnace walls, and throughwhich the evolved vaporous products are evacuated.

11. In an electric zinc distilling furnace, a horizontal septum orseptums disposed between the roof of the furnace and a resistor, andbeneath the resistor a trough containing the charge, the said septum orseptums being sloped toward a vertical flue o'r llues, whereby anycondensed metal collected thereon will flow to the charge.

12. An electric. zinc distilling furnace having a trough containing thecharge, a resistor above the charge, a ported horizontal septum orseptums above the resistor, a fume chamber above the septum or septumsand an inclosing cover whose rate of heat-radiation to atmosphere iscontrollable, whereby to increase or decrease the tempe'ature of thefume prior to its entering the condenser.

13. In an electric furnace, a chamber at whose bottom is a charge, asuspended radiating resistor above the charge and a suspendedseptum-casing within the chamber,

surrounding the top and sides of the resistor,whereby the resistor isfree to directly transmit heat to the charge but is enveloped by trappedvolatilized matter evolved therefrom.

14. An electric furnace having therein an open receptacle containing acharge which is being vaporized by radiant heat from an overlyingresistor, means for entrapping vapor whereby to envelop the resistor andnot be displaceable therefrom, and means for permitting the vaporevolved from the charge to flow horizontally along the lower portion ofthe trapped vapor and thence pass vertically upward through side-finesdisposed along the furnace.

15. An electric furnace having a radiating resistor enveloped innon-displaceable vapor directly received from an underlying openreceptacle containing the charge, and means for permitting thecontinuously evolved vapor to freely escape along the lower zone of saidenvelop and thence upwardly.

This specification signed and witnessed the 14th day of June, A. l).,1916, in the city of New York, borough of Manhattan, State of New York,by

JOHN THOMSON, and the 16 day of June A. 1)., 1916, at Niagara Falls,county of Niagara, and State New York, by

FRANCIS A. J. FITZ GERALD.

\Vitnesses for John Thomson:

\V. (l. MARGESON, M. F. Kna'rixo. 'itnesses for Francis A. J. FitzGerald:

R. H. \VARREN, H. M. VVARD.

